1. Field of the Invention
This invention relates to a method of producing a magnetic recording medium, and more particularly to a novel method of producing a magnetic recording medium by using a vapor deposition technique.
2. Description of the Prior Art
A coating type magnetic recording medium which is produced by dispersing a powdery magnetic recording material of .gamma.-Fe.sub.2 O.sub.3, .gamma.-Fe.sub.2 O.sub.3 doped with Co, Fe.sub.3 O.sub.4, CrO.sub.2 or a ferromagnetic alloy powder in an organic binder of vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, epoxy resin or polyurethane resin, coating the dispersion on a non-magnetic support, and drying the coating has been widely employed as a magnetic recording medium. Recently, with the increase in demand for high density recording, a ferromagnetic metal thin film, produced by methods that include electrical plating, electroless plating, sputtering, vacuum deposition and ion plating, has attracted the attention of many researchers as a so called a non-binder type magnetic recording medium, which does not employ a binder, and various efforts have been carried out for practical applications.
Since metal oxides with a lower saturation magnetic flux density (Bm) than that of ferromagnetic metals have mainly been used as magnetic materials, known coating type magnetic recording media have disadvantages in that reduction of the magnetic layer thickness required for high density recording approach a limit because a decrease in signal output occurs, in that their production processes are complicated, and in that a large scale of incidental facilities for the purpose of solvent recovery and pollution control are required therefor. Since thin films of ferromagnetic metals with a higher saturation magnetic flux density than that of metal oxides can be made without the need for the presence of non-magnetic materials such as binders, non-binder type magnetic recording media have the advantage that magnetic recording media with a very thin structure can be obtained for the purpose of high density recording. However, since non-binder type magnetic recording media are composed of continuous thin metal films where the electrical conductivity is increased, they may have the disadvantages that unwanted noise is generated and that the recording magnetization is decreased due to the eddy current generated when electrical signals are recorded on the media using a magnetic head. Further, since non-binder type magnetic recording media comprise continuous magnetic thin films, saw tooth transition regions may result when magnetic recording is performed. Therefore, these non-binder type magnetic recording media have the disadvantage that high density recording corresponding to a recording wavelength below the width of the magnetized transition regions is impossible. More further, incidental facilities for pollution control may be required for the fabrication of the non-binder type magnetic recording media when such are produced using plating techniques.